FIG. 1 schematically illustrates a partial cross section of an axial end of a conventional labyrinth seal bearing along an axial direction. As shown in FIG. 1, the bearing includes: an inner ring 1; an outer ring 2; and a labyrinth seal structure 3, located in a radial gap (not shown) between the inner ring 1 and the outer ring 2, wherein the bearing is sealed with the labyrinth seal structure at the axial end of the bearing.
The labyrinth seal structure 3 includes: a first seal ring 31, fixedly set with respect to the outer ring 2, wherein there is an clearance S1 between an inner periphery of the first seal ring 31 and the inner ring 1 along a radial direction; a second seal ring 32, including a first axial extension element 32b and a first radial extension element 32a, wherein the first axial extension element 32b extends along an axial direction and is fixed on an outer surface of the inner ring 1, the first radial extension element 32a extends from an end of the first axial extension element 32b along a radial outward direction; a third seal ring 33, fixedly set with respect to the first seal ring 31, including a second axial extension element 33b and a second radial extension element 33a, wherein the second axial extension element 33b extends along the axial direction, the second radial extension element 33a extends from an end of the second axial extension element 33b along a radial inward direction. The first radial extension element 32a is located between the first seal ring 31 and the second radial extension element 33a, there is a clearance (not shown) between the first radial extension element 32a and the second axial extension element 33b, and a clearance S2 between the second radial extension element 33a and the first axial extension element 32b. 
A labyrinth gap channel G is formed among the first seal ring 31, the second seal ring 32 and the third seal ring 33. The clearance S1 between the first seal ring 31 and the inner ring 1, and the clearance S2 between the second radial extension element 33a and the first axial extension element 32b form two ports of the labyrinth gap channel G, wherein the two ports are communicated with each other. One port of the two ports is communicated with an internal of the bearing, and the other port of the two ports is communicated with an external of the bearing. Wherein the internal of the bearing refers to a space surrounded by the inner ring 1, the outer ring 2 and the labyrinth seal structure 3, and the external of the bearing refers to an external environment where the bearing locates.
A standard for evaluating the sealing effect of a bearing is: the ability to prevent environmental contamination from entering the bearing, and the ability to prevent leakage of lubricant in the bearing. However, a contactless seal is realized in the conventional labyrinth seal bearing, which will result in a poor sealing effect.